SPN 110 FMI 16Medium-High
Engine Coolant Temperature - Moderately High (Warning)
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Connector Pinout — in guided session
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Overview
Fault Code
SPN 110 / FMI 16
Severity
Medium-High
Regen Inhibit
No
Inducement Risk
No
Component Location: Engine coolant temperature sensor is typically threaded into the engine block, cylinder head, or thermostat housing on the coolant outlet side of the engine.
Common Symptoms
- Engine coolant temperature warning light or gauge elevated
- High coolant temp alert in dashboard or driver display
- DPF regeneration inhibited or interrupted
- Possible engine power derate activated
- Coolant temp reading above normal operating range but below shutdown threshold
- Intermittent or sustained high temp warning with no visible overheating
Root Causes
- Low coolant level due to leak or evaporation
- Thermostat stuck closed or slow to open
- Clogged or restricted radiator cores
- Faulty or aerated coolant temperature sensor giving false high reading
- Failed or slipping coolant fan clutch not engaging properly
- Coolant pump wear or impeller failure reducing flow
- Air in cooling system causing hot spots
- Clogged coolant filter restricting flow
- Ambient temperature combined with high load conditions pushing temps high
- EGR cooler leak introducing exhaust into coolant circuit
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Derate Behavior
Mileage / Regen Notes
Active DPF regeneration may be inhibited or suspended when engine coolant temperature is moderately high to prevent additional thermal load; regen will resume once temperature returns to normal operating range.
System Interactions
SPN 110 FMI 16 interacts with the following systems and may trigger cascading faults if not resolved promptly.
TSB Reference: OEM cooling system TSBs
Common Diagnostic Mistakes
Replacing the sensor without verifying wiring continuity and supply voltage first.
Clearing codes without identifying and resolving the root cause — the fault will return.
Ignoring related active faults — cascading faults often share a root cause.
Skipping the connector inspection — corrosion and damaged pins are a leading cause of sensor faults.
Condemning the ECM before exhausting all wiring and component tests.
Related Faults in This Category
OEM System Resources
ASE Training Resources
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 110 FMI 16 — Full FSM Sequence & Repair Steps — includes wiring notes, sensor specs, and gated repair procedures.
Authority References
Diagnostic procedures on this page are informed by OEM service literature and industry standards.
Cummins QuickServe OnlineOfficial Cummins service manuals, fault code lookup, and TSB database.Detroit Diesel DiagnoCentralDetroit Diesel diagnostic procedures, DDDL documentation, and service literature.PACCAR MX Engine ServicePACCAR MX-11 and MX-13 engine service documentation and DAVIE diagnostic guides.Volvo/Mack Tech ToolVolvo and Mack engine fault code reference and PTT/Tech Tool diagnostic procedures.ASE — Diesel Truck Technician CertificationNational Institute for Automotive Service Excellence — T2 Diesel Engines certification standards.EPA Aftertreatment & Emissions GuidelinesU.S. EPA heavy-duty diesel aftertreatment compliance, DPF/SCR regulations, and NOx standards.
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